Macroscopic criteria for Green type porous materials with spheroidal voids: application to double porous materials

Combined effects of matrix plastic compressibility and void shape are investigated for ductile porous materials. To this end, a spheroidal volume containing a confocal spheroidal (prolate or oblate) void subjected to uniform strain rate boundary conditions has been first studied. A Green type matrix is chosen as a prototype for investigating effects of plastic compressibility. This is carried out by using a kinematics limit analysis theory from which a closed‐form expression of the macroscopic criterion is established for the considered class of materials. These results are then extended to ductile porous materials made up of a green matrix containing randomly oriented spheroidal voids. In the framework of a two‐step homogenization procedure, the obtained results are implemented to describe the macroscopic behavior of double porous materials involving spherical voids at the microscale and randomly oriented and distributed spheroidal voids at the mesoscale. For validation purpose, the new derived criteria are assessed and validated by comparing their predictions to available upper bounds and numerical data from literature. Copyright © 2017 John Wiley & Sons, Ltd.     

电偶源频率电磁测深中比值视电阻率和阻抗相位的联合反演

本文论述了电偶源频率电磁测深中,利用比值视电阻率和相应阻抗相位进行联合反演的必要性和可能的应用前景及具体实施方法。理论模型和实际观测资料的反演试验表明这一联合反演是可行和有效的,且明显地优于视电阻率和阻抗相位的单参量反演。     

A hypothesis for the seismogenesis of a double seismic zone

The seismogenesis of a double seismic zone, in particular the lower layer of a double seismic zone, has not been adequately explained in the literature. On the basis of seismic data and geothermal structures along three well-studied cross-sections in the Kuril-Kamchatka and Japan subduction zones, we investigate the temperature/pressure conditions associated with seismogenic structures of the double seismic zones. the corresponding T/P loci seem to suggest that earthquakes observed in the lower layer and in the lower part (below approximately 130 ± 20 km) of the top layer of a double seismic zone were caused by metastable phase transition-a mechanism similar to that responsible for deep-focus earthquakes only at lower temperature/pressure conditions. Under this hypothesis, the wedge-shaped configuration of a double seismic zone is interpreted to represent the loci of the kinetic boundary of the phase transition. According to theoretical/experimental studies and the constraints imposed by our observations, a likely candidate for such a phase transition is the metastable Al-rich enstatite decomposing into the assemblage of Al-poor enstatite plus garnet. Earthquakes in the upper part of the top layer were most probably due to conventional mechanisms such as dehydration of subducted materials and/or facies change from basalt to eclogite. That the top layer involves more than one seismogenic mechanism is also implied by the distinct behaviour of seismicity in the vicinity of 130 ± 20 km. Because the presence of deviatoric stress is critical to the reaction rate of a metastable phase transition, it is inferred that single seismic zones are also caused by the same mechanisms, except that the implicit layer of a supposed double seismic zone is missing, due to the insufficient amount of appropriate metastable minerals or to the lack of appropriate deviatoric stresses in the source region.     

Identification and occurrence of novel C36–C54 3,4-dialkylthiophenes with an unusual carbon skeleton in immature sediments

A series of novel long-chain 3,4-dialkylthiophenes (C₃₆–C₅₄) was identified in a number of sediments ranging from Pleistocene to Cretaceous. The identifications were based on mass spectral characterisation, desulphurisation and mass spectral data of synthesised model compounds. These organic sulphur compounds are probably formed by sulphur incorporation into mid-chain dimethylalkadienes with two methylenic double bonds. These putative precursor lipids are unprecedented and may be considered rather unusual. The distribution of 3,4-dialkylthiophenes in sediments varies considerably with the depositional palaeoenvironment, indicating that these compounds have a potential as molecular markers reflecting changes in palaeoenvironment.     

伊朗卡尔赫水电站坝址松散砾岩钻探工艺

在伊朗卡尔赫水电站坝址工程勘察中，采用金刚石双管单动钻具和ＳＭ胶冲洗液进行取样钻探，用清水钻进压水试验，由于钻探工艺合理，钻探质量均达到了设计要求。     

正交实验法在测绘中的应用

以检测数字水准仪及标尺综合精度为例，介绍了正交实验法在测绘领域中的应用。     

正交实验法在测绘仪器检定中的应用

在测绘生产和科研项目中，为了改革旧工艺或对新仪器，新产品,经常需要做多因素实验，如何安排多因素实验，是一个很值得研究的问题，文中以数字水准仪及标尺综合精度的检定为例，介绍了正交实验法在测绘仪器检定中的应用。